In a typical cellular radio frequency (RF) communications system such as a radiotelephone system, a base station employing transmitters and receivers (transceivers) establishes communication to mobile stations within a cell served by the base station. The cell served by the base station may include one or more sectors. Each sector generally includes at least one antenna for servicing one or more communications channels. Communications channels may be, for example, frequency channels, time slots within the same frequency such as in a Time Division Multiple Access (TDMA) system, or spread spectrum channels, as found in a Code Division Multiple Access (CDMA) system.
At the base station, RF signals may be routed between any one of a number of transceivers and a communications channel serviced by one of the sectors. An RF switch matrix which includes a number of individual switches and may be located on a matrix board having multiple switch matrices is generally utilized to direct the RF signals between the transceivers and the appropriate sectors.
An RF switch matrix's performance may be negatively affected by electrostatic discharge (ESD). ESD damage often occurs during shipping and handling prior to installation. For example, ESD may cause a switch within the switch matrix to remain in one position (i.e., either open or closed), or to fail to pass a signal, resulting in the misdirection or blockage of RF communications. Even if a switch matrix is operational when installed, ESD may have significantly shortened the switch matrix's life.
Thus, field engineers responsible for installing matrix boards containing switch matrices may be required to test each electrical path in each switch matrix manually, often using external RF equipment and complicated software.
One system for verifying the output of switch matrices utilized in RF communications systems is disclosed in U.S. Pat. No. 5,446,370 to Voight. The Voight patent teaches using external equipment including, among other things, a transceiver, a spectrum analyzer and a computer to determine whether an RF switch matrix directed any one of N RF signals to any one of M sectors. The determination is based on a predetermined power level of an input signal, a measured power of an output signal and a relationship between levels of attenuation in an attenuator bank.